The objective of this project is to study the feasibility of using iodinated liposomes as CT blood pool agents in nonhuman primates. Iopromide-containing liposomes were investigated as blood pool contrast agents for computed tomography (CT) in five normal adult baboons (15-21 kg). Liposomes (mean diameter = 195 nm) were injected intravenously at doses of 300 mg total iodine/kg (46% encapsulation) to each of five anesthetized adult baboons. The animals tolerated the injections well without measurable ECG changes and recovered uneventfully from anesthesia. Sequential helical CT scans from the base of the skull to the symphysis pubis acquired up to 40 min postinjection showed persistent blood pool enhancement. The maximum mean blood pool enhancement level was 106 HU at 1 min. Mean blood pool enhancement was 76 HU, 72 HU, and 67 HU at 10, 20, and 40 min, respectively. Liver and spleen were enhanced by 40 HU and 41 HU, respectively, at 40 min. No significant enhancement was measured in the brain and pancreas. Thus, iopromide-carrying liposomes containing soy phosphatidyl glycerol demonstrate prolonged vascular enhancement and are effective as blood pool CT contrast agents for CT in primates.